Bushing, Case, No Walk Out, 400, 4L80E, 4L85E, GM (65-UP)

The OEM case bushing in vehicles with a THM-400 or 4L80-E transmission tends to walk out of the housing bore. This allows the bushing to wander into the extension housing, leaves the output shaft unsupported, and may ruin the governor gear and cause case damage. The Sonnax case bushing 34006-SP is specially designed to remain in the case bore. When damage to the case is so severe that the standard size bushing 34006-SP cannot be installed, Sonnax offers an oversized case bushing. 34006-OS allows cases with damaged/scored bushing bores to be machined and salvaged.

Both bushings have a flange on the transmission case side that prevents them from pushing completely through the bore.
Flange accurately locates and helps retain the selective washer.
Machined oil grooves allow for a supply of lubricating oil to enter the extension housing as well as the transmission case.
Oversized bushing has an oversized outer diameter where it presses into the case.

Note: The case bore should be machined to 2.171/2.172" diameter to accept the oversized bushing.